Review fixes: telemetry session id per login; Framework number text

F1: the telemetry session id is new at every login. The original made one per
load of its assembly and its loader reloaded it at every login; the backend
counts new kills per (session id, character), so reusing one id across a
relog under-counted kills until the reset counter passed the old total.

F5/F6: .NET Framework never wrote a negative zero, and its fixed-point
formats (F7, F2, F0) rounded at fifteen significant digits, half away from
zero. Spawn and portal coordinates, kills_per_hour and the !report line now
format that way; the round-trip converter maps -0 to 0.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/OpenAC.MosswartMassacre.Tests/PluginLifecycleTests.cs

@@ -42,6 +42,21 @@ public sealed class PluginLifecycleTests
         Assert.Equal("Horan", harness.Context.Settings.CharacterName);
     }
 
+    [Fact]
+    public void Each_login_gets_a_new_telemetry_session_id()
+    {
+        // The backend counts new kills per (session id, character); the kill
+        // counter restarts at every login, so the id must too.
+        using var harness = new PluginHarness("Mossy");
+        harness.Login();
+        string first = harness.Context.TelemetrySessionId;
+
+        harness.Plugin.OnLogin();
+
+        Assert.NotEqual(first, harness.Context.TelemetrySessionId);
+        Assert.Equal(32, harness.Context.TelemetrySessionId.Length);
+    }
+
     [Fact]
     public void Mm_without_a_subcommand_prints_usage_and_unknown_is_reported()
     {